After a while of eating not enough food, what are symptoms like when your body starts getting to the "malnourished" point?

You can develop anaemia and other problems. Usually it's the macrocytic anaemia, which is the one caused by a lack of vitamins, particularly B12 and folic acid. You also get a "beer belly", because of the lack of vitamins and especially albumin, and men can develop prostate problems in particular, women and men can become demented.

It's also bad for your skin. You get a rougher skin. Long term, you can develop diabetes, because of the ups and downs in glycemia. Any more stuff you need to know, talk to your pharmacist or doctor, they would be happy to help.

Feeling tired, cold, constant headache.